Known in the art is British Patent No. 1,487,241 (Parker) filed on Feb. 6, 1974, which describes improvements relating to a transmission element. The transmission element consists of a pulley having a pair of plates mounted in opposed dispositions upon a shaft and rotatable by a belt in between to rotate the shaft. A liquid-tight cylinder secured to the second plate contains a piston fixed relative to the first plate and divides the cylinder in two chambers. A liquid in one chamber responds to centrifugal force resulting from the pulley rotation to move the second plate from the first to reduce the pulley diameter. A return spring in the other chamber returns the second plate as the centrifugal force is reduced and increases the diameter.
In U.S. Pat. No. 3,782,213 (Rattunde) issued on Jan. 1st, 1974, there is described an infinitely variable cone pulley transmission supplied with a pressure fluid entering through a passage in the transmission and that escapes therefrom through a narrow annular slot close to the shaft axis.
In U.S. Pat. No. 5,052,981 (Robert) issued on Oct. 1st, 1991, there is described a variable diameter pulley with centrifugal weights. This pulley has a movable cheek and a stationary cheek, where the movable cheek is forced toward the stationary cheek upon application of a centrifugal force. The centrifugal force acts on the weights that push the movable cheek.
In U.S. Pat. No. 5,108,347 (Gourdon) issued on Apr. 28, 1992, there is described a speed variator pulley provided with a transmission membrane. This pulley has a fixed cheek and a movable cheek, where as a shaft rotates, inertia blocks located in a reaction cup behind the movable cheek are subject to centrifugal forces which cause the movable cheek to move toward the fixed cheek.
In U.S. Pat. No. 5,145,464 (Mori) issued on Sep. 8, 1992, there is described a centrifugal oil pressure control device having a movable sheave and a fixed sheave, where the movable sheave is pushed away from the fixed sheave on application of a centrifugal force.